Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $174.54   4.387%   $182.1971   $182.20   $182.20   $182.20  
  Purchase #2 $184.59   4.772%   $193.3986   $193.40   $193.40   $193.40  
  Purchase #3 $96.92   4.386%   $101.1709   $101.17   $101.15   $101.20  
  Purchase #4 $44.93   4.529%   $46.9649   $46.96   $46.95   $47.00  
  Purchase #5 $69.81   10.515%   $77.1505   $77.15   $77.15   $77.20  
  Purchase #6 $104.30   8.155%   $112.8057   $112.81   $112.80   $112.80  
  Purchase #7 $40.90   4.357%   $42.682   $42.68   $42.70   $42.70  
  7 purchase totals = $715.99       $756.3697   $756.37   $756.35   $756.50